Napped artificial leather and composite material

ABSTRACT

Disclosed is a napped artificial leather including: a fiber-entangled body including ultrafine fibers having a fineness of 0.5 dtex or less; and an elastic polymer impregnated into the fiber-entangled body, the napped artificial leather having a thickness of 0.25 to 1.5 mm, and including a main surface that is a napped surface formed by napping the ultrafine fibers. The napped artificial leather further includes phosphorous-based flame retard ant particles attached to the elastic polymer such as a polyurethane, the phosphorous-based flame retardant particles being locally present in a range of a thickness of 200 pm or less from a back surface opposite to the main surface. The phosphorous-based flame retardant particles have an average particle size of 0.1 to 30 μm, a phosphorus atom content of 14 mass % or more, and a solubility in water at 30° C. of 0.2 mass % or less, and a melting point, or, in the absence of a melting point, a decomposition temperature, of 150° C. or more, and a content ratio of the phosphorous-based flame retardant particles is 1 to 6 mass % as a content ratio in terms of phosphorus atoms.

TECHNICAL FIELD

The present invention relates to a napped artificial leather having both flame retardancy and an excellent surface quality appearance, and a composite material using the same.

BACKGROUND ART

Conventionally, a napped artificial leather having an appearance resembling that of a suede leather has been known that is obtained by napping one surface of an artificial leather gray fabric in which a fiber-entangled body such as a non-woven fabric is impregnated with an elastic polymer. The napped artificial leather is used for the materials of shoes, clothing, gloves, bags, balls, and the like, and the interior materials for buildings and vehicles. The napped artificial leather is advantageous, for example, in that it is superior in quality stability, heat resistance, water resistance, and abrasion resistance, and also is easier to maintain, as compared with natural leathers such as a suede leather.

Meanwhile, in recent years, interior materials for which leather-like sheets such as synthetic leather sheets have been used as the interior materials for public transports such as aircrafts, vessels, and railroad vehicles, and the interior materials for public buildings such as hotels and department stores. The interior materials that are used in public places are required to have a high level of flame retardancy such as self-extinguishing properties, low smoke generation, and low heat generation in order to ensure safety in the event of a fire. In order to meet such flame retardancy requirements, halogen-based flame retardants having high flame retardancy performance have hitherto been widely blended in the interior materials. However, halogen-based flame retardants generate a toxic halogen gas when burned. Therefore, public organizations and users with environmental concerns have recommended that halogen-based flame retardants not be used. For instance, PTLs 1 to 4 listed below disclose techniques for using a phosphorous-based flame retardant and a metal hydroxide-based flame retardant in order to make leather-like sheets flame retardant.

CITATION LIST Patent Literatures

-   [PTL 1] Japanese Laid-Open Patent Publication No. 56-050985 -   [PTL 2] Japanese Laid-Open Patent Publication No. 2009-235628 -   [PTL 3] Japanese Laid-Open Patent Publication No. 2013-227685 -   [PTL 4] Japanese Laid-Open Patent Publication No. 2007-321280

SUMMARY OF INVENTION Technical Problem

A napped artificial leather obtained by impregnating an elastic polymer into voids inside a fiber-entangled body of ultrafine fibers having a fineness of less than 1 dtex has a smooth surface touch and an excellent quality appearance as compared with a napped artificial leather using a knitted or woven fabric of fibers having a fineness of about 1 to 5 dtex, which are also called regular fibers, as a base material. However a napped artificial leather including ultrafine fibers has a larger fiber surface area than that of a napped artificial leather including regular fibers, and therefore has lower flame retardancy.

It has been difficult to impart sufficient flame retardancy to a napped artificial leather including ultrafine fibers, without using a halogen-based flame retardant. Examples of the non-halogen-based flame retardant containing no halogen include a phosphorous-based flame retardant. Specific examples of the phosphorous-based flame retardant include polyphosphoric acid inorganic salts such as a polyphosphoric acid metal salt, ammonium polyphosphate, and carbamate polyphosphate, and phosphoric acid salts such as guanidine phosphate. However, polyphosphoric acid inorganic salts and phosphoric acid salts have relatively high water solubility, and therefore tend to be swollen or dissolved by moisture, water, or heat in the usage environments, or tend to bleed to the surface of the napped artificial leather when heat acts thereon through drying after they have been applied to the napped artificial leather. As a result of the flame retardant being swollen or dissolved, or bleeding to the surface of the napped artificial leather, the flame retardant causes whitening or coloring of the napped surface that is the main surface, thus impairing the surface quality appearance of the napped artificial leather. Although aromatic-containing phosphoric acid esters, and aliphatic phosphoric acid esters such as an aliphatic phosphonic acid ester and an aliphatic cyclic phosphonic acid ester have relatively low water solubility, they cannot provide sufficient effect of imparting flame retardancy, impair the texture of the napped artificial leather, or are likely to cause bleeding or the like.

It is an object of the present invention to provide a napped artificial leather including a fiber-entangled body of ultrafine fibers, wherein flame retardancy has been imparted to the napped artificial leather by using a non-halogen-based flame retardant without impairing the surface quality appearance, and also to provide a composite material using the napped artificial leather.

Solution to Problem

An aspect of the present invention is directed to a napped artificial leather including: a fiber-entangled body including ultrafine fibers having a fineness of 0.5 dtex or less; and an elastic polymer impregnated into the fiber-entangled body, the napped artificial leather having a thickness of 0.25 to 1.5 mm, and including a main surface that is a napped surface formed by napping the ultrafine fibers. The napped artificial leather further includes phosphorous-based flame retardant particles attached to the elastic polymer, the phosphorous-based flame retardant particles being locally present in a range of a thickness of 200 μm or less from a back surface opposite to the main surface.

The phosphorous-based flame retardant particles have an average particle size of 0.1 to 30 μm, preferably 0.5 to 30 μphosphorus atom content of 14 mass % or more, and a solubility in water at 30° of 0.2 mass % or less, and a melting point, or, in the absence of a melting point, a decomposition temperature, of 150° C. or more. Also, a content ratio of the phosphorous-based flame retardant particles is 1 to 6 mass % as a content ratio in terms of phosphorus atoms.

With such a napped artificial leather, it is possible to obtain a napped artificial leather to which flame retardancy has been imparted using a non-halogen-based flame retardant without impairing the surface quality appearance, by allowing the above-described phosphorous-based flame retardant particles to be locally present at a high concentration in a back surface constituting a surface opposite to a main surface that forms the appearance of a napped artificial leather including a fiber-entangled body of ultrafine fibers.

Preferably, the elastic polymer includes a polyurethane that is a reaction product of a polyurethane raw material including a polymer polyol, an organic polyisocyanate, and a chain extender, the polymer polyol includes 60 mass % or more of a polycarbonate polyol, and has an average number of repeating carbon atoms excluding a reactive functional group, of 6.5 or less, and the organic polyisocyanate includes at least one selected from the group consisting of 4,4′-dicyclohexylmethane diisocyanate and 4,4′-diphenylmethane diisocyanate.

Preferably, the napped artificial leather has a basis weight of 100 to 300 g/m².

As the phosphorous-based flame retardant particles, an organic phosphinic acid metal salt, an aromatic phosphoric acid ester, and a phosphoric acid ester amide are particularly preferable. In particular, it is preferable to include, as the phosphorous-based flame retardant particles, at least one selected from the group consisting of a dialkyl phosphinic acid metal salt and a monoalkyl phosphinic acid metal salt, because these are highly water resistant and heat resistant, have a high phosphorus atom content, and achieve high flame retardancy effect.

It is preferable that in the napped artificial leather, 90 to 100 mass % of the phosphorous-based flame retardant particles are present in the range of a thickness of 200 μm or less from the back surface of the napped artificial leather, because the surface quality appearance is further less likely to be impaired.

It is preferable that in the napped artificial leather, a content ratio of the phosphorous-based flame retardant particles in a total amount of the phosphorous-based flame retardant particles and the elastic polymer is 5 to 20 mass % in terms of phosphorus atoms, because the reduction in flame retardancy due to the elastic polymer can be sufficiently suppressed.

It is preferable that in the napped artificial leather, the elastic polymer includes the first elastic polymer that is present throughout a thickness cross section thereof, and a second elastic polymer that is locally present in the range of a thickness of 200 μm or less, and the phosphorous-based flame retardant particles are attached to the second elastic polymer, because the phosphorous-based flame retardant particles are likely to be locally present in the range of a thickness of 200 μm or less.

It is preferable that in the napped artificial leather, a content ratio of the phosphorous-based flame retardant particles in a total amount of the phosphorous-based flame retardant particles and the second elastic polymer is 10 to 30 mass % in terms of phosphorus atoms, because the effect of the second elastic polymer on the reduction in flame retardancy is reduced.

Another aspect of the present invention is directed to composite material obtained by bonding, to the back surface of any one of the napped artificial leathers, an interior backing material using an adhesive. Such a composite material has both flame retardancy and an excellent surface quality appearance as an interior material or an exterior material whose surface is decorated using the napped artificial leather.

For example, the above-described composite material can achieve a total heat release (THR) of 10 MJ/m² or less, a peak heat release rate (PHRR) of 250 kW/m² or less, or a maximum average rate of heat emission (MARHE) of 90 kW/m² or less.

Advantageous Effects of Invention

According to the present invention, it is possible to obtain a napped artificial leather including a fiber-entangled body of ultrafine fibers, wherein flame retardancy is imparted to the napped artificial leather using a non-halogen-based flame retardant without impairing the surface quality appearance, and a composite material using the napped artificial leather.

DESCRIPTION OF EMBODIMENT

A napped artificial leather according to the present embodiment is a napped artificial leather including: a fiber-entangled body including ultrafine fibers having a fineness of 0.5 dtex or less; and an elastic polymer impregnated into the fiber-entangled body, the napped artificial leather having a thickness of 0.25 to 1.5 mm, and including a main surface that is a napped surface formed by napping the ultrafine fibers. Also, the napped artificial leather further includes phosphorous-based flame retardant particles attached to the elastic polymer, the phosphorous-based flame retardant particles being locally present in a range of a thickness of 200 μm or less from a back surface opposite to the main surface.

The elastic polymer imparts shape stability to the fiber-entangled body, and imparts a quality appearance to the napped surface. Examples of the elastic polymer include polyurethane, an acrylonitrile elastomer, an olefin elastomer, a polyester elastomer, a polyamide elastomer, and an acrylic elastomer. These may be used alone or in a combination of two or more. Among these, polyurethane is preferable.

As the elastic polymer, it is particularly preferable to include a polyurethane that is a reaction product of a polyurethane raw material including a polymer polyol, an organic polyisocyanate, and a chain extender, the polymer polyol includes 60 mass % or more of a polycarbonate polyol, and has an average number of repeating carbon atoms excluding a reactive functional group, of 6.5 or less, and the organic polyisocyanate includes at least one selected from the group consisting of 4,4′-dicyclohexylmethane diisocyanate and 4,4′-diphenylmethane diisocyanate.

The phosphorous-based flame retardant particles have an average particle size of 0.1 to 30 μm, a phosphorus atom content of 14 mass % or more, a solubility in water at 30° C. of 0.2 mass % or less, a melting point, or, in the absence of a melting point, a decomposition temperature, of 150° C. or more. Also, the napped artificial leather contains 1 to 6 mass % of the phosphorous-based flame retardant particles as a content ratio in terms of phosphorus atoms.

The napped artificial leather can be obtained, for example, by a flame retardant treatment in which a treating liquid containing phosphorous-based flame retardant particles and a second elastic polymer is applied to a back surface opposite to a main surface of a napped artificial leather gray fabric including a fiber-entangled body including ultrafine fibers having a fineness of 0.5 dtex or less, and a first elastic polymer impregnated into the fiber-entangled body, and including the main surface that is a napped surface formed by napping the ultrafine fibers, and having a thickness of 0.25 to 1.5 mm, and thereafter the napped artificial leather gray fabric is dried, thus allowing the phosphorous-based flame retardant particles to be locally present in the region of a thickness of 200 μm or less from the back surface.

The napped artificial leather has a basis weight of preferably 100 to 600 g/m², more preferably 100 to 300 g/m², particularly preferably 170 to 300 g/m², and quite particularly preferably 170 to 250 g/m², because high flame retardancy can be sufficiently maintained, the phosphorous-based flame retardant particles are less likely to affect the appearance and the tactile impression of the napped surface, and the surface quality appearance is further less likely to be reduced.

Examples of the fiber-entangled body including ultrafine fibers having a fineness of 0.5 dtex or less include fiber structures such as a non-woven fabric, a woven fabric, and a knitted fabric including ultrafine fibers having a fineness of 0.5 dtex or less. Among these, a non-woven fabric of ultrafine fibers is particularly preferable because the homogeneity is increased, and therefore a napped artificial leather excellent in suppleness and fullness can be obtained. In the present embodiment, a non-woven fabric of ultrafine fibers will be described in detail as a representative example of the fiber-entangled body of ultrafine fibers.

Examples of the production method of the non-woven fabric of ultrafine fibers include a production method in which island-in-the-sea composite fibers are melt spun to produce a web, and the web is subjected to an entangling treatment, and thereafter the sea component is selectively removed from the island-in-the-sea composite fibers, to form ultrafine fibers. Examples of the production method of the web include a method in which filaments of the island-in-the-sea composite fibers that have been spun by spunbonding or the like are collected on a net, without being cut, to form a filament web, and a method in which filaments are cut into staples to form a staple web. Among these, a filament web is particularly preferable because of excellent denseness and excellent fullness. The formed web may be subjected to a fusion bonding treatment in order to impart shape stability thereto. Examples of the entangling treatment include a method in which about 5 to 100 layers of the web are placed on top of each other, and subjected to needle punching or a high-pressure water jetting treatment. In any of the processes until the sea component of the island-in-the-sea composite fibers is removed to form ultrafine fibers, a fiber shrinking treatment such as heat shrinking using water vapor may be performed, thus densifying the island-in-the-sea composite fibers to enhance the fullness.

Although the present embodiment describes in detail a case where the island-in-the-sea composite fibers are used, the non-woven fabric may be produced using ultrafine fiber-generating fibers other than the island-in-the-sea composite fibers, or to directly spin ultrafine fibers without using ultrafine fiber-generating fibers. As specific examples of the ultrafine fiber-generating fibers other than the island-in-the-sea composite fibers, any fibers capable of forming ultrafine fibers may be used without any particular limitation, including: for example, strip/division-type fibers in which a plurality of ultrafine fibers are lightly bonded immediately after spinning, and separated by a mechanical operation, to form a plurality of ultrafine fibers; and petal-shaped fibers obtained by alternately assembling a plurality of resins in a petal shape in a melt spinning process.

The island component resin of the island-in-the-sea composite fibers for forming the ultrafine fibers is not particularly limited. Specific examples thereof include: aromatic polyesters such as polyethylene terephthalate (PET), isophthalic acid-modified PET, sulfoisophthalic acid-modified PET, polybutylene terephthalate, and polyhexamethylene terephthalate; aliphatic polyesters such as polylactic acid, polyethylene succinate, polybutylene succinate, polybutylene succinate adipate, and a polyhydroxybutyrate-polyhydroxyvalerate resin; polyamides (nylons) such as 6-polyamide, polyamide 66, polyamide 10, polyamide 11, polyamide 12, and polyamide 6-12; and polyolefins such as polypropylene, polyethylene, polybutene, polymethylpentene, and a chlorine-based polyolefin. These may be used alone or in a combination of two or more. Among these, PET or modified PET, polylactic acid, polyamide 6, polyamide 12, polyamide 6-12, polypropylene, and the like are preferable.

As the sea component resin for forming the island-in-the-sea composite fibers, a resin that differs from the island component resin in solubility in a solvent or in decomposability in a decomposition agent is selected. Specific examples of the thermoplastic resin for forming the sea component include a water-soluble polyvinyl alcohol, polyethylene, polypropylene, polystyrene, an ethylene-propylene resin, an ethylene-vinyl acetate resin, a styrene-ethylene resin, and a styrene-acrylic resin.

The sea component of the island-in-the-sea composite fibers is removed by dissolution or decomposition at an appropriate stage after the web has been formed. Through such removal by decomposition or through dissolution and extraction, the island-in-the-sea composite fibers are subjected to ultrafine fiber generation, and ultrafine fibers in the form of fiber bundles are formed.

The fineness of the ultrafine fibers is 0.5 dtex or less, preferably 0.001 to 0.4 dtex, and more preferably 0.01 to 0.3 dtex. When the fineness of the ultrafine fibers exceeds 0.5 dtex, the quality appearance of the napped surface is likely to be reduced. As for the fineness, a cross section of the napped artificial leather in the thicknesses direction is imaged using a scanning electron microscope (SEM) at a magnification of 2000×, to obtain a cross-sectional area of single fibers, and the fineness of a single fiber can be calculated from the cross-sectional area and the specific gravity of the resin that forms the ultrafine fibers. The fineness can be defined as an average value of the fineness of average 100 single fibers, evenly obtained from the captured image.

The first elastic polymer is evenly applied into the entire non-woven fabric. The first elastic polymer restrains ultrafine fibers, thus imparting shape stability to the fiber-entangled body including ultrafine fibers having a fineness of 0.5 dtex or less, and providing a quality appearance to the napped surface. Examples of the first elastic polymer include polyurethane, an acrylonitrile elastomer, an olefin elastomer, a polyester elastomer, a polyamide elastomer, and an acrylic elastomer. These may be used alone or in a combination of two or more. Among these, polyurethane is preferable.

Note that polyurethane tends to be more flammable than ultrafine fibers. In the napped artificial leather according to the present embodiment, the deterioration in appearance of the napped surface due to application of a flame retardant can be suppressed by applying the flame retardant to the back surface side of the napped artificial leather.

In the case of using polyurethane, it is particularly preferable to use a specific polyurethane because the flame retardancy of the napped surface can be improved.

Such a specific polyurethane includes a polyurethane that is a reaction product of a polyurethane raw material including a polymer polyol, an organic polyisocyanate, and a chain extender, the polymer polyol includes 60 mass % or more of a polycarbonate polyol, and has an average number of repeating carbon atoms excluding a reactive functional group, of 6.5 or less, and the organic polyisocyanate includes at least one selected from the group consisting of 4,4′-dicyclohexylmethane diisocyanate and 4,4′-diphenylmethane diisocyanate. Such a polyurethane is excellent in self-extinguishing properties, has reduced heat release and smoke generation, and exhibits a high level of flame retardancy.

Specific examples of the polycarbonate polyol include polycarbonate polyols such as polyhexamethylene carbonate diol, poly(3-methyl-1,5-pentylene carbonate) diol, polypentamethylene carbonate diol, polytetramethylene carbonate diol, and polycyclohexane carbonate diol, and copolymers thereof.

The polymer polyol may include a polymer polyol other than the polycarbonate polyol in a range that does not exceed 40 mass % of the polymer polyol. Specific examples of the polymer polyol other than the polycarbonate polyol include polyether polyols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and poly(methyl tetramethylene glycol), and copolymers thereof; polyester polyols such as polyethylene adipate diol, poly(l,2-propylene adipate)diol, poly(l,3-propylene adipate)diol, polybutylene adipate diol, polybutylene sebacate diol, polyhexamethylene adipate diol, poly(3-methyl-1,5-pentane adipate)diol, poly(3-methyl-1,5-pentane sebacate)diol, and polycaprolactone diol, and copolymers thereof; polycarbonate polyols having 6.5 or more carbon atoms; and polyester carbonate polyols. These may be used alone or in a combination of two or more.

The content ratio of the polycarbonate polyol included in the polymer polyol used for production of the specific polyurethane is 60 mass % or more, and is preferably 70 mass % or more. When the content ratio of the polycarbonate polyol included in the polymer polyol is less than 60 mass %, the heat release and the smoke generation of the polyurethane increase.

The average number of repeating carbon atoms excluding a reactive functional group, of the polymer polyol used for production of the specific polyurethane is 6.5 or less, and is preferably 6.0 or less. When the average number of repeating carbon atoms excluding a reactive functional groups, of the polymer polyol exceeds 6.5, the hear release and the smoke generation of the polyurethane also increase.

Here, the average number of repeating carbon atoms excluding a reactive functional group, of the polymer polyol is defined as the number of carbon atoms in a hydrocarbon included in the repeating units of the polymer polyol, including a carbonate group (—OCOO—), an ester group (—COO—), an ether group (—O—), or the like in a reaction for forming the polymer polyol, excluding a reactive functional group. The average number of repeating carbon atoms excluding a reactive functional group in the case where two or more polymer polyols are used is a value obtained by calculating the average value of the number of carbon atoms in a hydrocarbon included in the repeating units of the two or more polymer polyols including carbonate groups, ester groups, ether groups, or the like, excluding a reactive functional group.

As the molecular weight of the polymer polyol, the polymer polyol has an average molecular weight of preferably 200 to 6000, and more preferably 500 to 5000.

The organic polyisocyanate used for production of the specific polyurethane includes at least one selected from the group consisting of 4,4′-dicyclohexylmethane diisocyanate and 4,4′-diphenylmethane diisocyanate. Preferably 60 mass % or more, more preferably 70 mass % or more, and particularly preferably 80 mass % or more of the organic polyisocyanate includes at least one selected from the group consisting of 4,4′-dicyclohexylmethane diisocyanate and 4,4′-diphenylmethane diisocyanate, because a polyurethane exhibiting excellent self-extinguishing properties and having reduced heat release and smoke generation can be obtained.

For the polyurethane raw material, a multifunctional alcohol such as a trifunctional alcohol and a tetrafunctional alcohol, and a short-chain alcohol such as ethylene glycol may be used in addition to the polymer polyol. These may be used alone or in a combination of two or more.

For the polyurethane raw material, another organic isocyanate may also be used in addition to 4,4′-dicyclohexylmethane diisocyanate and 4,4′-diphenylmethane diisocyanate. Specific examples of such an organic isocyanate include non-yellowing diisocyanates, including, for example, aliphatic or alicyclic diisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, and norbornene diisocyanate; and aromatic diisocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, and xylylene diisocyanate polyurethane. If necessary, a multifunctional isocyanate such as a trifunctional isocyanate or a tetrafunctional isocyanate, and a blocked multifunctional isocyanate may also be used. These may be used alone or in a combination of two or more.

As the chain extender used for production of the specific polyurethane, a low-molecular weight compound having two or more active hydrogens can be used. Specific examples of the chain extender include diamines such as hydrazine, ethylene diamine, propylene diamine, hexamethylene diamine, nonamethylene diamine, xylylene diamine, isophorone diamine, piperazine and derivatives thereof, adipic acid dihydrazide, and isophthalic acid dihydrazide; triamines such as diethylenetriamine; tetramines such as triethylene tetramine; diols such as ethylene glycol, propylene glycol, 1,4-butane diol, 1,6-hexane diol, 1,4-bis(β-hydroxyethoxy)benzene, and 1,4-cyclohexane diol; triols such as trimethylol propane; pentaols such as pentaerythritol; amino alcohols such as amino ethyl alcohol and amino propyl alcohol. These may be used alone or in a combination of two or more. Among these, it is preferable to use a combination of two or more from hydrazine, piperazine, ethylenediamine, hexamethylene diamine, isophoronediamine, and derivatives thereof, triamine such as diethylenetriamine, and ethylene glycol, propylene glycol, 1,4-butane diol, and derivatives thereof, because of the excellent mechanical properties. Monoamines such as ethylamine, propylamine, and butylamine; carboxyl group-containing monoamine compounds such as 4-amino butanoic acid and 6-amino hexanoic acid; monools such as methanol, ethanol, propanol, and butanol may be used together with the chain extender during a chain extending reaction. Among these, a chain extender having six or less carbon atoms excluding a reactive functional group is particularly preferable because of the excellent self-extinguishing properties and the reduced heat release and smoke generation.

In order to control the water absorption ratio, the adhesion with ultrafine fibers, and the hardness of polyurethane, a crosslinked structure may be formed in the polyurethane by adding a crosslinking agent containing, in the molecule, two or more functional groups capable of reacting with a functional group included in monomer units that form the polyurethane, such as a carbodiimide-based compound, an epoxy-based compound, an oxazoline-based compound, or a self-crosslinking compound such as a polyisocyanate-based compound and a multifunctional block isocyanate compound.

Examples of the emulsion of the polyurethane include a forcedly emulsified polyurethane emulsion that does not include any ionic group in the polyurethane skeleton and has been emulsified by adding an emulsifier; a self-emulsified polyurethane emulsion that includes an ionic group such as a carboxyl group, a sulfonic acid group, and an ammonium group in the polyurethane skeleton and has been emulsified by self-emulsification; and a polyurethane emulsion that uses an emulsifier and an ionic group in the polyurethane skeleton in combination. Examples of the method for introducing a carboxyl group into the polyurethane skeleton include a method in which units of carboxyl group-containing diols such as 2,2-bis(hydroxymethyl)propionic acid, 2,2-bis(hydroxymethyl)butanoic acid, and 2,2-bis(hydroxymethyl)valeric acid are incorporated into the polyurethane skeleton.

The first elastic polymer is applied to the fiber-entangled body, for example, by impregnating a fiber-entangled body of ultrafine fibers-generating fibers such as island-in-the-sea composite fibers for forming ultrafine fibers, or a fiber-entangled body of ultrafine fibers with an emulsion of an elastic polymer such as a polyurethane emulsion or a solution of an elastic polymer such as a polyurethane solution, followed by coagulation. Examples of the method for impregnating the fiber-entangled body with the emulsion or solution of the first elastic polymer include methods using a knife coater, a bar coater, or a roll coater, and a method involving dipping. In the case of using an emulsion, the elastic polymer can be coagulated by a method in which heating is performed in a drying device at 50 to 200° C., a method in which heating is performed in a dryer after infrared heating, a method in which heating is performed in a dryer after a steam treatment, a method in which heating is performed in a dryer after ultrasonic heating, or a combination of these methods.

As the emulsion of the polyurethane, it is preferable to use a self-emulsified polyurethane and a forcedly emulsified polyurethane in combination, and it is preferable to use a polyurethane emulsion including, for example, 20 to 100 mass % of a self-emulsified polyurethane and 0 to 80 mass % of a forcedly emulsified polyurethane, because a flexible texture can be achieved. The average dispersed particle size of the emulsion of the polyurethane is preferably 0.01 to 1 μm, and more preferably 0.03 to 0.5 μm.

When the fiber-entangled body is impregnated with the emulsion of the polyurethane, and thereafter dried, the emulsion may migrate to the surface layer of the fiber-entangled body, and may thus become less likely to be uniformly applied in the thickness direction. In such a case, for example, it is possible to suppress the migration in the following manner. Adjusting the dispersed particle size of the emulsion; adjusting the type and the amount of the ionic group in the polyurethane; reducing the water dispersion stability by addition of an ammonium salt that undergoes a pH change at a temperature of about 40 to 100° C.; or reducing the water dispersion stability by addition of a monovalent or divalent alkali metal salt or alkaline-earth metal salt, a nonionic emulsifier, an associative water-soluble thickener, an associative heat-sensitive gelling agent such as a water-soluble silicone-based compound, or a water-soluble polyurethane-based compound.

The first elastic polymer has a 100% modulus of preferably 0.5 to 7 MPa, and more preferably 1 to 5 MPa, because a flexible texture can be obtained, and smooth surface and surface physical properties can be imparted. When the 100% modulus is too low, the first elastic polymer is softened to restrain the ultrafine fibers when the napped artificial leather is subjected to heat, so that the flexible texture and the smooth surface touch tends to be reduced. When the 100% modulus is too high, the smooth surface touch of the napped artificial leather tends to be reduced, and the texture may be hard.

The ratio of the first elastic polymer included in the napped artificial leather is preferably 3 to 50 mass %, more preferably 3 to 40 mass %, particularly preferably 3 to 35 mass %, and quite particularly preferably, 7 to 25 mass %, in terms of the well-balanced high flame retardancy, surface quality appearance, shape stability, and surface physical properties.

The fiber-entangled body containing the first elastic polymer is subjected to a heat-moisture shrinking treatment or pressed as needed so that the apparent density, the basis weight, or the thickness thereof is adjusted, and thus is finished into an artificial leather gray fabric. Then, the artificial leather gray fabric is sliced as needed. Then, at least one surface of the artificial leather gray fabric is buffed using a contact buff or an emery buff, thus producing a napped artificial leather gray fabric including a napped surface.

It is preferable that the buffing is performed using sandpaper or emery paper with a grit number of about 120 to 600, for example. By raising the fibers on the surface that has been buffed in this manner, a napped artificial leather gray fabric including a napped surface formed by napping the ultrafine fibers is produced. The napped artificial leather gray fabric may be further subjected to a finishing treatment such as a dyeing treatment, a flexibilizing treatment by crumpling, a softening treatment by milling, a reverse seal brushing treatment, an antifouling treatment, a hydrophilization treatment, a lubricant treatment, a softener treatment, an antioxidant treatment, an ultraviolet absorber treatment, and a fluorescent agent treatment, as needed.

The thickness of the napped artificial leather gray fabric is substantially equal to the thickness of the resulting final napped artificial leather. The thickness of the napped artificial leather gray fabric is 0.25 to 1.5 mm, preferably 0.3 to 1.0 mm, and more preferably 0.4 to 1.0 mm. When the thickness of the napped artificial leather gray fabric exceeds 1.5 mm, sufficient flame retardancy effect is less likely to be achieved.

The napped artificial leather can be obtained by a flame retardant treatment, which is a treatment in which a treating liquid containing phosphorous-based flame retardant particles and a second elastic polymer is applied to a back surface opposite to the napped surface that is a main surface of the napped artificial leather gray fabric having a thickness of 0.25 to 1.5 mm, and thereafter dried, thus allowing the phosphorous-based flame retardant particles to be locally present in a range of a thickness of 200 μm or less from the back surface.

Here, allowing the phosphorous-based flame retardant particles to be locally present in a range of a thickness of 200 μm or less from a back surface opposite to the main surface in the napped artificial leather means that the majority of the phosphorous-based flame retardant particles present in the napped artificial leather, specifically, 90 to 100 mass %, more particularly 95 to 100 mass %, of the phosphorous-based flame retardant particles are present in the range of a thickness of 200 μm or less from the back surface opposite to the main surface. The thickness from the back surface in which the phosphorous-based flame retardant particles are locally present, opposite to the main surface is preferably 50 to 200 μm, more preferably 70 to 180 μm, and particularly preferably 100 to 150 μm. The thickness of the region of the napped artificial leather in which the phosphorous-based flame retardant particles are locally present can be confirmed by observing a cross section of the napped artificial leather that is parallel to the thickness direction thereof using a scanning electron microscope. The ratio of the thickness of the region in which the phosphorous-based flame retardant particles are locally present to the overall thickness of the napped artificial leather is preferably 10 to 60%, and more preferably 10 to 50%, because a high level of flame retardancy can be easily imparted using a non-halogen-based flame retardant without impairing the surface quality appearance.

In this manner, by allowing the phosphorous-based flame retardant particles to be locally present in the range of a thickness of 200 μm or less from the back surface of the napped artificial leather such that the content ratio in terms of phosphorus atoms is 1 to 6 mass %, it is possible to impart flame retardancy using a non-halogen-based flame retardant without impairing the surface quality appearance.

The content ratio, in the napped artificial leather, of the phosphorous-based flame retardant particles locally present in the range of a thickness of 200 μm or less from the back surface of the napped artificial leather is 1 to 6 mass %, and preferably 1.5 to 5.5 mass %, in terms of phosphorus atoms. When the content ratio of the phosphorous-based flame retardant particles in terms of phosphorus atoms is less than 1 mass %, a high level of flame retardancy is less likely to be achieved. When the content ratio of the phosphorous-based flame retardant particles in terms of phosphorus atoms exceeds 6 mass %, it is difficult to allow the phosphorous-based flame retardant particles to be locally present in the range of a thickness of 200 μm or less from the back surface by fixing the phosphorous-based flame retardant particles without causing them to fall off. Additionally, the suppleness of the napped artificial leather may be lost, or the surface quality appearance thereof may be reduced.

The phosphorous-based flame retardant particles included in the napped artificial leather are particles of a flame retardant compound that contains phosphorus atoms, and is a particulate solid at room temperature, the flame retardant compound having an average particle size of 0.1 to 30 μm, a phosphorus atom content of 14 mass % or more, a solubility in water at 30° C. of 0.2 mass % or less, a melting point, or, in the absence of a melting point, a decomposition temperature, of 150° C. or more.

The average particle size of the phosphorous-based flame retardant particles is 0.1 to 30 μm, preferably 0.5 to 30 μm, more preferably 0.5 to 15 μm, and particularly preferably 1 to 10 μm. When the average particle size exceeds 30 μm, the phosphorous-based flame retardant particles are less likely to be sufficiently infiltrated in the range of a thickness of 200 μm or less from the back surface of the napped artificial leather such that the content ratio of the phosphorous-based flame retardant particles is 1 to 6 mass % as a content ratio in terms of phosphorus atoms, so that the flame retardancy effect tends to be insufficient. When the average particle size is less than 0.1 μm, the particles are likely to aggregate and thus are unevenly dispersed, so that the flame retardancy is likely to be nonuniform.

The phosphorus atom content of the phosphorous-based flame retardant particles is 14 mass % or more, preferably 15 mass % or more, and more preferably 20 mass % or more. Also, the phosphorus atom content is preferably 30 mass % or less, and more preferably 28 mass % or less. When the phosphorus atom content of the phosphorous-based flame retardant particles is less than 14 mass %, a high level of flame retardancy is less likely to be imparted. When the phosphorus atom content of the phosphorous-based flame retardant particles is too high, the flame retardant is likely to fall off to be attached to the surface, and tends to adversely affect the surface appearance and the fastness.

The phosphorous-based flame retardant particles have a solubility in water at 30° C. of 0.2 mass % or less, and is preferably 0.15 mass % or less. When the phosphorous-based flame retardant particles having a solubility in water at 30° C. exceeding 0.2 mass % are used, the phosphorous-based flame retardant particles are likely to absorb moisture during production or in use, or bleed to the napped surface when wetted with water. Note that the solubility in water at 30° C. of the phosphorous-based flame retardant particles can be measured by adding the phosphorous-based flame retardant particles in small portions to 100 g of water at 30° C., and measuring a maximum mass of the phosphorous-based flame retardant particles that can be dissolved.

The phosphorous-based flame retardant particles have a hot-water solubility in hot water at 90° C. of preferably 5 mass % or less, and more preferably 3 mass % or less, because the flame retardant is less likely to bleed to the napped surface when the flame retardant comes into contact with hot water during production or in use of the napped artificial leather, and the dimensional change of the napped artificial leather caused by the flame retardant absorbing moisture can be suppressed. Note that the hot-water solubility in hot water at 90° C. of the phosphorous-based flame retardant particles can be measured by adding the phosphorous-based flame retardant particles in small portions to 100 g of water at 90° C., and measuring a maximum mass of the phosphorous-based flame retardant particles that can be dissolved.

The phosphorous-based flame retardant particles are particulate solids at room temperature that have a melting point, or, in the absence of a melting point, a decomposition temperature, of 150° C. or more, and preferably 200° C. or more. When the melting point, or, in the absence of a melting point, the decomposition temperature is less than 150° C., it is difficult to maintain the particulate form due to softening of the flame retardant in a drying process performed after application of the flame retardant during the production of the napped artificial leather. As a result, the phosphorous-based flame retardant particles bundle up the ultrafine fibers, resulting in a reduction in the surface touch and the texture of the napped surface. In addition, the napped artificial leather is likely to form a molten drop when burnt, thus making it difficult to maintain a high level of flame retardancy.

Here, the melting point of the phosphorous-based flame retardant particles can be specified by a melting peak temperature as determined by thermogravimetry-differential thermal analysis (TG-DTA), or differential scanning calorimetry (DSC). The decomposition temperature in the absence of a melting point can be specified by a decomposition starting temperature as determined by thermogravimetry-differential thermal analysis (TG-DTA). Although the measurement conditions are not particularly limited, measurement is performed at a temperature rising rate of 5 to 10° C./min under a nitrogen atmosphere.

Examples of the phosphorous-based flame retardant particles include organic phosphinic acid metal salts such as a dialkyl phosphinic acid metal salt and a monoalkyl phosphinic acid metal salt; aromatic phosphonic acid esters; and phosphoric acid ester amides. These may be used alone or in a combination of two or more. Among these, a dialkyl phosphinic acid metal salt or a monoalkyl phosphinic acid metal salt is preferable in that they are highly water resistant and heat resistant, have a high phosphorus atom content, and achieve high flame retardancy effect.

The second elastic polymer used for fixing the phosphorous-based flame retardant particles included in the napped artificial leather may be the same as, or different from the first elastic polymer. Among these, polyurethane is preferable because of the well-balanced physical properties.

The second elastic polymer has a 100% modulus of preferably 0.5 to 5 MPa, and more preferably 1 to 4 MPa, because a flexible texture can be achieved, and detachment of the flame retardant can be suppressed.

There is no particular limitation on the method for applying the treating liquid containing the phosphorous-based flame retardant particles and the second elastic polymer to the back surface of the napped artificial leather gray fabric having a thickness of 0.25 to 1.5 mm. Specific examples thereof include methods involving applying the treating liquid containing the phosphorous-based flame retardant particles and the second elastic polymer to the back surface of the napped artificial leather gray fabric by gravure coating, direct coating, roll coating, or spray coating while adjusting the application amount or the viscosity.

The viscosity of the treating liquid containing the phosphorous-based flame retardant particles and the second elastic polymer is preferably 200 to 10000 mPa·sec, and more preferably 500 to 5000 mPa·sec, because the phosphorous-based flame retardant particles and the second elastic polymer are likely to be allowed to sink moderately from the back surface of the napped artificial leather gray fabric so as to be locally present in the range of a thickness of 200 μm or less, thus making it possible to impart high flame retardancy to the napped artificial leather without impairing the quality appearance of the napped surface that is the main surface.

As the treating liquid containing the second elastic polymer, it is preferable to use, for example, a treating liquid prepared by dispersing the phosphorous-based flame retardant particles in a polyurethane emulsion. In the case of using a polyurethane emulsion, the average particle size of the emulsion is preferably 10 μm or less, and more preferably 5 μm. The drying temperature of the treating liquid is preferably 100 to 160° C.

The content ratio of the phosphorous-based flame retardant particles in the total amount of the phosphorous-based flame retardant particles and the second elastic polymer is preferably 10 to 30 mass %, more preferably 12 to 30 mass %, and particularly preferably 15 to 25 mass %, in terms of phosphorus atoms. It is preferable that the content ratio of the phosphorous-based flame retardant particles in the total amount of the phosphorous-based flame retardant particles and the second elastic polymer is the above-described ration, because the effect of burning of the second elastic polymer on the reduction in flame retardancy is reduced.

The content ratio of the phosphorous-based flame retardant particles in the total amount of the phosphorous-based flame retardant particles and the second elastic polymer is preferably in the range of 10 to 30 mass % in terms of phosphorus atoms, and is preferably 60 to 90 mass %, and more preferably 70 to 85 mass %, as the mass of the phosphorous-based flame retardant particles.

The ratio of the second elastic polymer included in the napped artificial leather is not particularly limited, but is preferably 2 to 15 mass %, and more preferably 4 to 10 mass %, because it is possible to sufficiently fix the phosphorous-based flame retardant particles while suppressing the reduction in flame retardancy due to application of the second elastic polymer.

When the ultrafine fibers form fiber bundles derived from island-in-the-sea composite fibers, the elastic polymer may be impregnated inside the fiber bundles, or may be attached to the outside of the fiber bundles. When island-in-the-sea composite fibers are subjected to an ultrafine fiber-generating treatment, the thermoplastic resin serving as the sea component is removed from the island-in-the-sea composite fibers, to form voids inside the ultrafine fiber bundles. Therefore, the second elastic polymer that is applied after subjecting the island-in-the-sea composite fibers to the ultrafine fibers-generating treatment is likely to be impregnated inside the fiber bundles to restrain the ultrafine fibers that form the fiber bundles. Accordingly, the second elastic polymer impregnated inside the ultrafine fiber bundles restrains the ultrafine fiber bundle, thus contributing to improvement of the shape retainability of the fiber-entangled body.

The ratio of the total amount of the elastic polymer including the first elastic polymer and the second elastic polymer included in the napped artificial leather is preferably 2 to 40 mass %, and more preferably 5 to 35 mass %, because it is possible to reduce the effect of burning of the polyurethane on the reduction of the flame retardancy.

The content ratio of the phosphorous-based flame retardant particles in the total amount of the phosphorous-based flame retardant particles and the elastic polymer including the first elastic polymer and the second elastic polymer is preferably 5 to 20 mass %, and more preferably 6 to 20 mass %, in terms of phosphorus atoms, because this provides a good balance between the flame retardancy and the suppleness of the napped artificial leather.

The total basis weight of the elastic polymer including the first elastic polymer and the second elastic polymer contained in the napped artificial leather is preferably 10 to 150 g/m², more preferably 10 to 100 g/m², and particularly preferably 10 to 50 g/m², because a napped artificial leather particularly well-balanced between the self-extinguishing properties and the surface quality appearance can be obtained.

The napped artificial leather may be subjected to softening for the purpose of smoothing the surface touch while improving the surface smoothness. Examples of softening include a method in which the napped artificial leather is brought into close contact with an elastic sheet and mechanically shrunk in a vertical direction (MD on production line), and then heated in the shrunk state for heat setting.

The thickness of the napped artificial leather is 0.25 to 1.5 mm, preferably 0.3 to 1.0 mm, and more preferably 0.4 to 1.0 mm. When the thickness of the napped artificial leather is less than 0.25 mm, the flame retardant is likely to be exposed on the surface, resulting in a reduction in the surface quality and the surface touch. When the thickness of the napped artificial leather exceeds 1.5 mm, the flame retardancy is reduced.

The apparent density of the napped artificial leather is preferably 0.25 to 0.75 g/cm³, and more preferably 0.35 to 0.65 g/cm³, because this increases the fiber density of the surface, provides favorable napped feel and surface touch of the napped surface, and well-balanced fullness and flexible texture.

The napped artificial leather can also be suitably used, for example, as a wall covering material formed by attaching the napped artificial leather and an interior backing material (back board) together using an adhesive for composites. Specific examples of the interior backing material include concrete, brick, a clay tile, a ceramic tile, a fiber-reinforced cemented board, a glass fiber cemented board, a calcium silicate board, steel, aluminum, a metal plate, glass, mortar, plaster, stone, a plaster board, rock wool, a glass wool board, a cemented excelsior board, a hard cemented excelsior board, a cemented excelsior board, a pulp cemented board, and flame-retardant plywood. Among these, concrete, brick, a clay tile, a ceramic tile, a fiber-reinforced cemented board, a glass fiber cemented board, a calcium silicate board, steel, aluminum, a metal plate, and glass are preferable because they can suppress the flammability when combined with the napped artificial leather.

Examples of the adhesive for composites include a starch-based adhesive, an (alkyl)cellulose-based adhesive, a vinyl acetate-based adhesive, an ethylene vinyl acetate-based adhesive, an acrylic resin-based adhesive, a polyurethane-based adhesive, a chloroprene-based adhesive, a phenol-based adhesive, a nitrile-based adhesive, an ester-based adhesive, a silicone-based adhesive, a fluorine-based adhesive, and copolymers and mixtures thereof, or adhesives in which a metal compound such as a metal salt or a hydroxide is mixed. Among these, a starch-based adhesive, an (alkyl)cellulose-based adhesive, a vinyl acetate-based adhesive, a chloroprene-based adhesive, a phenol-based adhesive, a nitrile-based adhesive, a fluorine-based adhesive, a silicone-based adhesive, and copolymers and mixtures thereof, and adhesives in which a metal salt or a hydroxide is mixed are preferable, because they can suppress the flammability when combined with the napped artificial leather.

The flame retardancy of a composite material obtained by bonding an interior backing material to the back surface of the napped artificial leather using an adhesive can be evaluated using a cone calorimeter in accordance with ISO 5660-1. Examples of the flame retardancy evaluated by a burn test using the cone calorimeter include a total heat release (THR; MJ/m²) due to combustion, a peak heat rate of release (PHRR; kW/m²) per unit area and unit time due to combustion, and a maximum average rate of heat emission (MARHE; kW/m²).

The composite material obtained by bonding an interior backing material to the back surface of the napped artificial leather using an adhesive makes it possible to realize a composite material having a total heat release (THR) of 10 MJ/m² or less, and even 8 MJ/m² or less. The composite material according to the present embodiment makes it possible to realize a composite material having a peak heat release rate (PHRR) of 250 kW/m² or less, and even 200 kW/m² or less. The composite material according to the present embodiment makes it possible to realize a composite material having a maximum average rate of heat emission (MARHE; kW/m²) of 90 kW/m² or less.

The napped artificial leather has a combination of a high level of flame retardancy, a surface quality appearance, a flexible texture, and fullness, and therefore can be suitably used in applications for which a high level of flame retardancy such as self-extinguishing properties, low heat generation, and low smoke generation is required, including, for example, the materials of seats and sofas or the interior materials of walls and the like of public transports such as aircrafts, vessels, railroad vehicles, and vehicles, or public buildings such as hotels and department stores.

EXAMPLES

Hereinafter, the present invention will be described more specifically by way of examples. It should be appreciated that the scope of the present invention is by no means limited by the examples.

First, the evaluation methods used in the present examples will be summarized.

(Surface Quality Appearance)

The napped surface of the napped artificial leather was touched, and evaluated according to the following criteria.

A: The surface touch was smooth, and also had no rough tactile impression caused by the phosphorous-based flame retardant particles.

B: The surface touch was rough, and was inferior in quality appearance.

C: The surface had a hard texture, and was inferior in quality appearance.

D: The phosphorous-based flame retardant particles had bled during storage, resulting in whitening of the surface.

(Thickness, Basis Weight, Apparent Density)

The thickness (mm) and the basis weight (g/cm²) of the napped artificial leather were measured in accordance with JIS L 1913, and the apparent density (g/cm³) was calculated by dividing the basis weight by the thickness, and converting the value into an apparent density.

(Measurement of Thickness of Region in Which Phosphorous-Based Flame Retardant Particles Attached to Elastic Polymer are Locally Present)

The napped artificial leather was cut out in the thickness direction, ten points were evenly selected from the entire cross section in the thickness direction, and the thickness of the region in which the phosphorous-based flame retardant particles were present from the back surface was measured at each of the ten points using a scanning electron microscope at a magnification of 100×. Then, an average value of the thicknesses at eight points, excluding a maximum value and a minimum value, was determined as the thickness in which the phosphorous-based flame retardant particles were locally present.

(Average Particle Size of Phosphorous-Based Flame Retardant Particles)

The napped artificial leather was cut out in the thickness direction, ten points were evenly selected from the entire cross section in the thickness direction, the region in which the phosphorous-based flame retardant particles were present from the back surface was selected using a scanning electron microscope at a magnification of 1000×, and the diameters of ten particles were measured. Then, an average value of the particle sizes of eight particles, excluding a maximum value and a minimum value, was determined as the average particle size of the phosphorous-based flame retardant particles.

(Vertical Burn Test: Self-Extinguishing Properties)

The napped artificial leather was subjected to a measurement of the vertical flame retardancy in accordance with the burn test standard for U.S. aircraft interior materials, prescribed in FAR 25, Appendix F, Part 1(a) (1) (ii). Specifically, the napped artificial leather was cut to a size of 50.8 mm×304.8 mm, to form a test piece. Then, the test piece was perpendicularly fixed to a sample holder of a burn test apparatus. A burner was disposed directly below an end of the test piece, and the flame was brought into contact with the test piece for 12 seconds, and thereafter the burn distance, the self-extinguishing time, the drop self-extinguishing time of the test piece were measured. An average for n=10 was calculated.

(Horizontal Burn Test)

The napped artificial leather was subjected to a horizontal burn test in accordance with the burn test prescribed in FMVSS 302. Specifically, the napped artificial leather was cut into 102 mm×356 mm, and a marked line was drawn at 38 mm from one end of the resulting sample, to form a test piece. Then, the test piece was fixed horizontally to a sample holder of a burn test apparatus. A burner was disposed at the sample end of the test piece sample on which the marked line was drawn, and the flame was brought into contact with the test piece for 15 seconds. Thereafter, the burn distance and the burn time of the test piece were measured. An average for n=10 was calculated. The test piece was evaluated as self-extinguished-before-marked line (SE) if the test piece had self-extinguished before the flame reached the marked line, evaluated as self-extinguished if the flame had passed the marked line and the test piece had a burn distance of 50 mm or less and a burn time of 60 seconds or less, evaluated as slow-burning if the test piece had a burn rate of 100 ram/min or less, and evaluated as flammable if the test piece had a burn rate of 100 ram/min or more.

<Evaluation of Composite Material Obtained by Making Napped Artificial Leather Composite>

A composite material obtained by making the napped artificial leather composite was evaluated according to the following evaluation methods.

(Combustion Heat Release Test)

As an interior material for wall covering, a composite material was produced by bonding the napped artificial leather to a calcium silicate board having a thickness of 11 mm and a density of 870 kg/m³ using a starch-vinyl acetate-based adhesive (solid content: 65 g/m2). This composite material was heated/burned for 20 minutes using a heater at 50 kW/m² in accordance with the cone calorimeter method prescribed in ISO 5660-1, and the total heat release (THR) after 20 minutes, the peak heat release rate (PHRR), the time for which the peak heat value exceeded 200 kW, and the maximum average rate of heat emission (MARHE) were measured.

(Combustion Smoke Test)

As an interior material for wall covering, a composite material was produced by bonding the napped artificial leather to a calcium silicate board having a thickness of 11 mm and a density of 870 kg/m³ using a starch-vinyl acetate-based adhesive (solid content: 65 g/m²). This composite material was heated/burned for 20 minutes using a heater at 50 kW/m² in accordance with the cone calorimeter method prescribed in ISO 5660-1, and the smoke production rate (SPR) was measured.

Example 1

Island-in-the-sea composite fibers were melt spun using a water-soluble thermoplastic polyvinyl alcohol (PVA) as a sea component resin, and an isophthalic acid-modified polyethylene terephthalate as an island component resin. Specifically, the molten resin of each of the sea component resin and the island component resin was supplied to a multicomponent fiber spinning spinneret having nozzle holes disposed for forming a cross section on which 25 island component resin portions were distributed in the sea component resin, and molten fibers of the island-in-the-sea composite fibers were discharged from the nozzle holes. At this time, the molten resins were supplied while adjusting the pressure such that the mass ratio between the sea component and the island components satisfied Sea component/Island component =25/75.

Then, the molten fibers of the island-in-the-sea composite fibers were stretched by suction using a suction apparatus, thus spinning island-in-the-sea composite fibers having a fineness of 3.3 dtex. The spun island-in-the-sea composite fibers were continuously piled on a movable net, and then lightly pressed with a heated metal roll, to suppress the fuzzing on the surface. Then, the island-in-the-sea composite fibers were removed from the net, and thereafter allowed to pass between the metal roll and a back roll, to hot press the fibers, thus obtaining a web having a basis weight of 31 g/m².

Next, the web was laid in eight layers using a cross lapper apparatus so as to have a total basis weight of 300 g/m², and then needle-punched alternately from both sides thereof, to entangle the web. The basis weight of the entangled web, which was the needle-punched web, was 440 g/m².

Then, the entangled web was allowed to undergo heat-moisture shrinking for 30 seconds at 70° C. and a humidity of 50% RH. The area shrinkage before and after the heat-moisture shrinking treatment was 47%.

Then, the shrunk entangled web was impregnated with an emulsion of a first polyurethane (first elastic polymer) including ammonium sulfate as a gelling agent, and thereafter dried. The first polyurethane was a self-emulsified amorphous polycarbonate urethane that had a 100% modulus of 3.0 MPa, and that was a reaction product of a polymer polyol including 100% of a polycarbonate polyol and having an average number of repeating carbon atoms excluding a reactive functional group, of 6, an organic polyisocyanate, which was 4,4′-dicyclohexylmethane diisocyanate, and a chain extender.

Then, the entangled web to which the first polyurethane had been applied was immersed in hot water to remove the PVA by dissolution, thus forming an artificial leather gray fabric including a non-woven fabric in which fiber bundles each including 25 ultrafine fibers having a fineness of 0.1 dtex were three-dimensionally entangled. The first polyurethane content of the artificial leather gray fabric was 12 mass %.

Then, the artificial leather gray fabric was sliced into halves in the thickness direction, and the surface opposite to the sliced surface was buffed, thus finishing the gray fabric into a napped artificial leather gray fabric including a suede-like napped surface. The napped artificial leather gray fabric had a thickness of 0.5 mm, a basis weight of 250 g/m2, and an apparent density of 0.50 g/cm³.

Then, the napped artificial leather gray fabric was dyed using a circular dyeing machine, and dried, and, thereafter, was impregnated with a softener, and further dried.

Then, using a gravure coating machine including a 35-mesh gravure roll, a second polyurethane emulsion of 2000 mPa·sec in which particles of a dialkyl phosphinic acid metal salt serving as a phosphorous-based flame retardant were dispersed was applied at 110 g/m² to the sliced surface of the dyed nappe artificial leather gray fabric, and the moisture was dried at 120° C. Note that the dialkyl phosphinic acid metal salt particles had a dispersed particle size (median diameter: D₅₀) of 4 μm, as measured by a laser diffraction/scattering particle size distribution measurement apparatus, a phosphorus atom content of 23.5 mass %, a solubility in water at 30° C. of less than 0.2 mass %, and a melting point and a decomposition temperature exceeding 250° C.

The second polyurethane emulsion contained 10 mass % of the second polyurethane (second elastic polymer) and 28 mass % of the dialkyl phosphinic acid metal salt. The second polyurethane was a forcedly emulsified amorphous polycarbonate urethane that had a 100% modulus of 1.0 MPa, and that was a reaction product of a polymer polyol including 100% of a polycarbonate polyol and having an average number of repeating carbon atoms excluding a reactive functional group, of 5.5, an organic polyisocyanate, which was 4,4′-dicyclohexylmethane diisocyanate, and a chain extender.

Then, the napped artificial leather gray fabric that had been subjected to the flame retardant treatment was shrunk in the vertical direction (length direction) by 5.0% by being subjected to a shrinkage processing treatment at a drum temperature 120° C. and a transport speed of 10 m/min, and thereafter the surface thereof was subjected to a sealing treatment, thus obtaining a napped artificial leather including a suede-like napped surface. The napped artificial leather had a thickness of 0.52 mm, a basis weight of 290 g/m², and an apparent density of 0.56 g/cm³.

The napped artificial leather contained 10 mass % of the first polyurethane, 5 mass % of the second polyurethane, and 15 mass % of the dialkyl phosphinic acid metal salt particles. As a result, the napped artificial leather contained 2.6 mass % of the dialkyl phosphinic acid metal salt as a content ratio in terms of phosphorus atoms. The mass % in terms of phosphorus atoms to the total amount of the dialkyl phosphinic acid metal salt particles, the first polyurethane, and the second polyurethane was 10.3 mass %. The mass % in terms of phosphorus atoms to the total amount of the second polyurethane and the dialkyl phosphinic acid metal salt particles was 17.3 mass %.

Then, the obtained napped artificial leather was evaluated according to the following evaluation methods.

The results of the above evaluation are shown in Table 1 below.

TABLE 1 Example No. 1 2 3 4 5 6 7 8 9 10 11 Ultrafine Fineness 0.1 0.1 0.1 0.1 0.4 0.2 0.2 0.4 0.001 0.1 0.1 fibers (dtex) Resin PET PET PET PET PET PET PET PET Ny PET PET First Average 6 6 6 6 4.9 6 6 4.9 4.9 6 5 poly- number of urethane repeating carbon atoms of polymer polyol Ratio of 100 100 100 100 60 100 100 75 75 100 0 polycarbon- ate in polymer polyol (mass %) Diiso- H-MDI H-MDI H-MDI H-MDI MDI H-MDI H-MDI MDI/H- MDI H-MDI IPDI cyanate MDI component* Content 10 9 19 11 10 10 9 20 31 10 19 ratio (C) (mass %) Second Content 5 11 5 3 5 4 4 3 5 5 5 poly- ratio (D) urethane (mass %) Total basis weight 42 55 78 37 39 42 38 98 102 11.3 62 of first polyurethane and second poly- urethane (g/m²) Phos- Compound Dialkyl Dialkyl Dialkyl Dialkyl Monoalkyl Aromatic Phos- Dialkyl Dialkyl Dialkyl Dialkyl phorous- phos- phos- phos- phos- phos- phos- phor- phos- phos- phos- phos- based phin- phin- phin- phin- phin- phin- ic acid phin- phin- phin- phin- flame ic acid ic acid ic acid ic acid ic acid ic acid ester ic acid ic ester ic acid ic acid retardant metal metal metal metal metal ester amide metal metal metal metal particles salt salt salt salt salt salt salt salt salt Content 15 14 13 9 15 15 17 7 14 15 9 ratio (E) (mass %) Dispersed 4 4 4 4 0.5 5 20 4 4 4 4 particle size (D₅₀: μm) Water <0.2% <0.2% <0.2% <0.2% <0.1% <0.1% <0.1% <0.1% <0.1% <0.2% <0.2% solubility (%: 30° C.) Melting >250° >250° >250° C. >250° >250° C. >250° C. >250° >250° >250° C. >250° >250° C. point, or C. C. C. C. C. C. decom- position temper- ature in the absence of melting point (° C.) Phosphorus 23.5 23.5 23.5 23.5 28 15 17 23.5 23.5 23.5 23.5 atom content (mass %) (F) Content ratio of 17.3 13.2 17.3 17.3 21.8 11.1 14 17.3 17.3 17.3 17.3 phosphorus atoms of phosphorous-based flame retardant particles in total amount of phosphorous-based flame retardant particles and second elastic polymer ((E) * (F)/((D) + (E))) (mass %) Content ratio of 10.3 8.6 6.9 7.8 12.6 6.6 8.6 5.8 5.6 6.0 7.6 phosphorus atoms of phosphorous-based flame retardant particles in total amount of phosphorous-based flame retardant particles, first elastic polymer, and second elastic polymer ((E) * (F)/ ((C) + (D) + (E)) (mass %) Content ratio in terms 2.6 2.5 2.4 1.6 3.1 1.6 2.2 1.7 2.7 1.0 1.5 of phosphorus atoms (E) * (F)/100 (mass %) Phosphorous- 4 4 4 4 0.5 5 20 4 4 4 4 based flame retardant average particle size (SEM: μm) Thickness from back 150 150 120 180 100 180 80 150 180 150 150 surface in which phosphorous-based flame retardant particles and second elastic polymer are present (L: μm) Thickness of napped 0.52 0.53 0.54 0.51 0.5 0.5 0.53 0.75 0.65 1.3 0.52 artificial leather (T: mm) Ratio of thickness L to 29 28 22 35 20 36 15 20 28 12 29 thickness T (%) Basis weight (g/m²) 290 300 320 275 280 280 300 435 280 725 290 Apparent density 0.56 0.56 0.59 0.54 0.56 0.56 0.57 0.58 0.43 0.56 0.56 (g/cm³) Surface quality A A A A A A A A A A A appearance Vertical Burn 100 115 105 105 90 110 110 80 110 120 230 burn test distance (self- (mm) extin- Self- 1 3 2.5 1 1 1 2 3.5 1 6 28 guishing extin- proper- guishing ties) time (sec) Drop self- 0 0 0 0 0 0 0 0 0 1.0 26 extin- guishing time (sec) Horizon- Burn rate SE SE SE SE SE SE SE SE SE SE Slow- tal burn burning test *H-MDI_4,4′-dicyclohexylmethane diisocyanate MDI_4,4′-diphenylmethane diisocyanate IPDI_isophorone diisocyanate

Example 2

A napped artificial leather was obtained in the same manner as in Example 1 except that a second polyurethane emulsion containing 22 mass % of the second polyurethane and 28 mass % of the dialkyl phosphinic acid metal salt was used in place of the second polyurethane emulsion containing 10 mass % of the second polyurethane and 28 mass % of the dialkyl phosphinic acid metal salt, and the obtained napped artificial leather was evaluated. The results are shown in Table 1.

Example 3

A napped artificial leather was obtained in the same manner as in Example 1 except that an artificial leather gray fabric having a first polyurethane content of 24 mass % was used in place of the artificial leather gray fabric having a first polyurethane content of 12 mass %, and the obtained napped artificial leather was evaluated. The results are shown in Table 1.

Example 4

A napped artificial leather was obtained in the same manner as in Example 1 except that the second polyurethane emulsion in which the dialkyl phosphinic acid metal salt particles serving as the phosphorous-based flame retardant were dispersed was applied at 60 g/m², instead of being applied at 110 g/m², and the obtained napped artificial leather was evaluated. The results are shown in Table 1.

Example 5

In Example 1, a non-woven fabric in which fiber bundles each including 6 ultrafine fibers of 0.4 dtex were three-dimensionally entangled was formed in place of the non-woven fabric in which fiber bundles each including 25 ultrafine fibers of 0.1 dtex were three-dimensionally entangled. In addition, as the first polyurethane, a self-emulsified amorphous polycarbonate urethane was used that had a 100% modulus of 3.0 MPa, and that was a reaction product of a polymer polyol having a mass ratio between an amorphous polycarbonate (average number of repeating carbon atoms excluding a reactive functional group: 5.5) and a polyether polyol (average number of repeating carbon atoms excluding a reactive functional group: 4) of 60/40 and an average number of repeating carbon atoms excluding a reactive functional group, of 4.9, an organic polyisocyanate, which was 4,4′-diphenylmethane diisocyanate, and a chain extender. Furthermore, the monoalkyl phosphinic acid metal salt shown in Table 1 was used in place of the dialkyl phosphinic acid metal salt as the phosphorous-based flame retardant particles. Otherwise, a napped artificial leather was obtained in the same manner as in Example 1, and the obtained napped artificial leather was evaluated. The results are shown in Table 1.

Example 6

In Example 1, a non-woven fabric in which fiber bundles each including ultrafine fibers of 0.2 dtex were three-dimensionally entangled was formed in place of the non-woven fabric in which fiber bundles each including 25 ultrafine fibers of 0.1 dtex were three-dimensionally entangled. In addition, the aromatic phosphoric acid ester shown in Table 1 was used in place of the dialkyl phosphinic acid metal salt as the phosphorous-based flame retardant particles. Otherwise, a napped artificial leather was obtained in the same manner, and the obtained napped artificial leather was evaluated. The results are shown in Table 1.

Example 7

In Example 1, a non-woven fabric in which fiber bundles each including ultrafine fibers of 0.2 dtex were three-dimensionally entangled was formed in place of the non-woven fabric in which fiber bundles each including 25 ultrafine fibers of 0.1 dtex were three-dimensionally entangled. In addition, the phosphoric acid ester amide shown in Table 1 was used in place of the dialkyl phosphinic acid metal salt as the phosphorous-based flame retardant particles. Otherwise, a napped artificial leather was obtained in the same manner, and the obtained napped artificial leather was evaluated. The results are shown in Table 1.

Example 8

Island-in-the-sea composite fibers were melt spun using polyethylene as a sea component resin, and an isophthalic acid-modified polyethylene terephthalate as an island component resin. Specifically, the molten resin of each of the sea component resin and the island component resin was supplied to a multicomponent fiber spinning spinneret having nozzle holes disposed for forming a cross section on which 25 island component resin portions were distributed in the sea component resin, and molten fibers of the island-in-the-sea composite fibers were discharged from the nozzle holes. At this time, the molten resins were supplied while adjusting the pressure such that the mass ratio between the sea component and the island components satisfied Sea component/Island component =25/75.

Then, the molten fibers of the island-in-the-sea composite fibers were stretched by suction using a suction apparatus, thus spinning island-in-the-sea composite fibers. The spun island-in-the-sea composite fibers were continuously piled on a movable net, and then lightly pressed with a heated metal roll, to suppress the fuzzing on the surface. Then, the island-in-the-sea composite fibers were removed from the net, and thereafter allowed to pass between the metal roll and a back roll, to hot press the fibers, thus obtaining a web.

Next, the web was laid in eight layers using a cross lapper apparatus so as to have a total basis weight of 320 g/m², and then needle-punched alternately from both sides thereof, to entangle the web. Then, the entangled web was allowed to undergo heat-moisture shrinking for 30 seconds at 70° C. and a humidity of 50% RH.

Then, the shrunk entangled web was impregnated with an N,N-dimethylformamide solution of the first polyurethane, and thereafter immersed in a liquid mixture of N,N-dimethylformamide and water for coagulation. Thereafter, the polyethylene was extracted with toluene, and dried. Note that the first polyurethane was an amorphous polycarbonate urethane that had a 100% modulus of 5.0 MPa, and that was a reaction product of a polymer polyol having a mass ratio between a polycarbonate polyol (average number of repeating carbon atoms excluding a reactive functional group: 6) and a polyester polyol (average number of repeating carbon atoms excluding a reactive functional group: 4) of 75/25, and having an average number of repeating carbon atoms excluding a reactive functional group, of 4.9, an organic polyisocyanate, which was 4,4′-diphenylmethane diisocyanate, and a chain extender.

Otherwise, a napped artificial leather was obtained in the same manner as in Example 1, and the obtained napped artificial leather was evaluated. The results are shown in Table 1.

Example 9

Island-in-the-sea composite fibers were melt spun using polyethylene as a sea component resin, and 6-nylon (6-polyamide) as an island component resin. Specifically, polyethylene and 6-nylon were mixed at a mass ratio of 50/50, and molten, and the molten resins were supplied to a blend spinning spinneret, and discharged from the nozzle holes. The average number of islands of the resulting fibers was approximately 600, and the fibers were stretched, to give fibers of 5.5 dtex. The fibers were crimped, and thereafter cut into 51 mm and carded, thus obtaining a staple web having a basis weight of 100 g/m². This web was laid in six layers using a cross lapper apparatus, to form a superposed web, and an oil solution was sprayed thereto, and thereafter the web was needle punched at a density of 1500 punch/cm2, followed by hot pressing, to obtain a fiber-entangled body having an apparent density of 0.40 g/cm³ and a thickness of 1.5 mm.

Then, the fiber-entangled body was impregnated with an N,N-dimethylformamide solution of the first polyurethane, and thereafter immersed in a liquid mixture of N,N-dimethylformamide and water for coagulation. Thereafter, the polyethylene was extracted with toluene, and dried. Note that the first polyurethane was a polyurethane that had a 100% modulus of 5.0 MPa, and that was a reaction product of a polymer polyol having a mass ratio between a polycarbonate polyol (average number of repeating carbon atoms excluding a reactive functional group: 6) and a polyester polyol (average number of repeating carbon atoms excluding a reactive functional group: 4) of 75/25, and having an average number of repeating carbon atoms excluding a reactive functional group, of 4.9, an organic polyisocyanate, which was 4,4′-diphenylmethane diisocyanate, and a chain extender. Otherwise, a napped artificial leather was obtained in the same manner as in Example 1 except that the dye was changed from the disperse dye to a metal complexed dye, and the obtained napped artificial leather was evaluated. The results are shown in Table 1.

Example 10

A napped artificial leather was obtained in the same manner as in Example 1 except that an artificial leather gray fabric having a thickness of 1.3 mm was used, and the obtained napped artificial leather was evaluated. The results are shown in Table 1.

Example 11

A napped artificial leather was obtained in the same manner as in Example 3 except that the first elastic polymer was changed to a polyether-based polyurethane (average number of repeating carbon atoms excluding a reactive functional group: 5), and that the content ratio (E) of the phosphorous-based flame retardant particles was changed from 13 mass % to 9 mass %, and the obtained napped artificial leather was evaluated. The results are shown in Table 1.

Comparative Example 1

A napped artificial leather was obtained in the same manner as in Example 1 except that a second polyurethane emulsion containing 10 mass % of the second polyurethane and 6.8 mass % of the dialkyl phosphinic acid metal salt was used in place of the second polyurethane emulsion containing 10 mass % of the second polyurethane and 28 mass % of the dialkyl phosphinic acid metal salt, and the obtained napped artificial leather was evaluated. Note that the viscosity of the aqueous dispersion including the phosphorous-based flame retardant particles and the second polyurethane was 100 mPa·sec. The results are shown in Table 2.

TABLE 2 Comparative Example No. 1 2 3 4 5 Ultrafine Fineness (dtex) 0.1 0.1 0.1 0.1 0.6 fibers Resin PET PET PET PET PET First Average number of repeating 6 6 6 6 9 polyurethane carbon atoms of polymer polyol Ratio of polycarbonate in 100 100 100 100 100 polymer polyol (mass %) Diisocyanate component* H-MDI H-MDI H-MDI H-MDI HD Content ratio (C) (mass %) 11 10 10 10 19 Second Content ratio (D) (mass %) 6 0 5 5 5 polyurethane Total basis weight of first polyurethane and 33 22 33 33 62 second polyurethane (g/m²) Phosphorous- Compound Dialkyl Ammonium Ammonium Aromatic Dialkyl based flame phosphinic polyphosphate polyphosphate phosphoric phosphinic retardant acid acid acid particles metal salt ester metal salt Content ratio (E) (mass %) 4 15 15 15 9 Dispersed particle size (D₅₀: μm) 4 20 20 0.5 4 Water solubility (%: 30° C.) <0.2% 0.5 0.5 <0.2% <0.2% Melting point, or >250° C. >250° C. >250° C. 115° C. >250° C. decomposition temperature in the absence of melting point (° C.) Phosphorus atom content 23.5 31 31 10 23.5 (mass %) (F) Content ratio of phosphorus atoms of 9.5 31 22.8 7.4 17.3 phosphorous-based flame retardant particles in total amount of phosphorous-based flame retardant particles and second elastic polymer ((E) * (F)/((D) + (E))) (mass %) Content ratio of phosphorus atoms of 3.7 16 13.5 4.4 7.8 phosphorous-based flame retardant particles in total amount of phosphorous-based flame retardant particles, first elastic polymer, and second elastic polymer ((E) * (F)/((C) + (D) + (E))) (mass %) Content ratio in terms of phosphorus atoms 0.7 3.5 3.4 1.1 1.6 (E) * (F)/100 (mass %) Phosphorous-based flame retardant average 4 20 20 Non- 4 particle size (SEM: μm) particulate Thickness from back surface in which 300 100 100 200 150 phosphorous-based flame retardant particles and second elastic polymer are present (L: μm) Thickness of napped artificial leather (T: mm) 0.52 0.51 0.52 0.5 0.52 Ratio of thickness L to thickness T (%) 58 20 19 40 29 Basis weight (g/m²) 260 270 290 280 290 Apparent density (g/cm³) 0.5 0.53 0.56 0.56 0.56 Surface quality appearance B B, D C, D C A Vertical burn Burn distance (mm) 260 120 150 280 280 test (self- Self-extinguishing 30 9 11 40 40 extinguishing time (sec) properties) Drop self- 8 0 4 20 30 extinguishing time (sec) Horizontal Burn rate Slow- Self- Self- Slow- Slow- burn test burning extinguished extinguished burning burning *H-MDI_4,4′-dicyclohexylmethane diisocyanate MDI_4,4′-diphenylmethane diisocyanate HD_1,6-hexamethylene diisocyanate

Comparative Example 2

A napped artificial leather was obtained in the same manner as in Example 1 except that an aqueous dispersion containing 28 mass % of ammonium polyphosphate was used in place of the second polyurethane emulsion containing 10 mass % of the second polyurethane and 28 mass % of the dialkyl phosphinic acid metal salt, and the obtained napped artificial leather was evaluated. The results are shown in Table 2.

Comparative Example 3

A napped artificial leather was obtained in the same manner as in Example 1 except that the ammonium polyphosphate shown in Table 2 was used in place of the dialkyl phosphinic acid metal salt as the phosphorous-based flame retardant particles, and the obtained napped artificial leather was evaluated. The results are shown in Table 2.

Comparative Example 4

A napped artificial leather was obtained in the same manner as in Example 1 except that the aromatic phosphoric acid ester shown in Table 2 was used in place of the dialkyl phosphinic acid metal salt as the phosphorous-based flame retardant particles, and the obtained napped artificial leather was evaluated. The results are shown in Table 2. Note that the phosphorous-based flame retardant was treated in the form of an aqueous dispersion during the flame retardant treatment. However, as a result of observation of the napped artificial leather, the phosphorous-based flame retardant had formed a resin film, and was not in the particulate form.

Comparative Example 5

A napped artificial leather was obtained in the same manner as in Example 4 except that ultrafine fibers having an average fineness of 0.6 dtex produced by changing the number of the island components formed with the spinneret from 25 to 4, and that the first elastic polymer was changed to a polycarbonate-based polyurethane (average number of repeating carbon atoms excluding a reactive functional group: 9), and the obtained napped artificial leather was evaluated. The results are shown in Table 2.

Referring to Tables 1 and 2, all of the napped artificial leathers obtained in Examples 1 to 11 had favorable surface quality appearance, a flexible texture, and flame retardancy. Furthermore, the napped artificial leathers obtained in Example 1 to 10 had favorable self-extinguishing properties, reduced smoke generation and combustion heat release, and a very high level of flame retardancy. On the other hand, in the case of the napped artificial leather obtained in Comparative Example 1, which included a smaller amount of the phosphorous-based flame retardant particles, and in which the flame retardant particles were present even in the interior, the phosphorous-based flame retardant was exposed on the surface, resulting in deterioration in the surface quality appearance. In the case of the napped artificial leather obtained in Comparative Example 2, which used ammonium polyphosphate as the phosphorous-based flame retardant particles, bleeding had occurred over time, resulting in deterioration in the surface quality appearance. In the case of the napped artificial leather obtained in Comparative Example 3, bleeding had occurred over time, resulting in deterioration in the surface quality appearance. Comparative Example 4, in which the phosphorous-based flame retardant particles were changed to the aromatic phosphoric acid ester, had a hard texture.

Example 12

Island-in-the-sea composite fibers were melt spun using PVA as a sea component resin, and an isophthalic acid-modified polyethylene terephthalate as an island component resin. Specifically, the molten resin of each of the sea component resin and the island component resin was supplied to a multicomponent fiber spinning spinneret having nozzle holes disposed for forming a cross section on which 25 island component resin portions were distributed in the sea component resin, and molten fibers of the island-in-the-sea composite fibers were discharged from the nozzle holes. At this time, the molten resins were supplied while adjusting the pressure such that the mass ratio between the sea component and the island components satisfied Sea component/Island component =25/75.

Then, molten fibers of the island-in-the-sea composite fibers were stretched by suction using a suction apparatus, thus spinning island-in-the-sea composite fibers having a fineness of 3.3 dtex. The spun island-in-the-sea composite fibers were continuously piled on a movable net, and then lightly pressed with a heated metal roll, to suppress the fuzzing on the surface. Then, the island-in-the-sea composite fibers were removed from the net, and thereafter allowed to pass between the metal roll and a back roll, to hot press the fibers, thus obtaining a web having a basis weight of 31 g/m2.

Next, the web was laid in eight layers using a cross lapper apparatus so as to have a total basis weight of 250 g/m², and then needle punched alternately from both sides thereof, to entangle the web. The basis weight of the entangled web, which was the needle punched web, was 350 g/m².

Then, the entangled web was allowed to undergo heat-moisture shrinking for 30 seconds at 70° C. and a humidity of 50% RH. The area shrinkage before and after the heat-moisture shrinking treatment was 47%.

Then, the shrunk entangled web was impregnated with an emulsion of a first polyurethane including ammonium sulfate as a gelling agent, and thereafter dried. The first polyurethane was a self-emulsified amorphous polycarbonate urethane having a 100% modulus of 3.0 MPa and including 4,4′-dicyclohexylmethane diisocyanate as the diisocyanate component.

Then, the entangled web to which the first polyurethane had been applied was immersed in hot water to remove the PVA by dissolution, thus forming an artificial leather gray fabric including a non-woven fabric in which fiber bundles each including 25 ultrafine fibers having a fineness of 0.1 dtex were three-dimensionally entangled. The first polyurethane content of the artificial leather gray fabric was 12 mass %.

Then, the artificial leather gray fabric was sliced into halves in the thickness direction, and the surface opposite to the sliced surface was buffed, thus finishing the gray fabric into a napped artificial leather gray fabric including a suede-like napped surface. The napped artificial leather gray fabric had a thickness of 0.35 mm, a basis weight of 175 g/m², and an apparent density of 0.50 g/cm³.

Then, the napped artificial leather gray fabric was dyed using a circular dyeing machine, and dried, and, thereafter, was impregnated with a softener, and further dried.

Then, using a gravure coating machine including a 35-mesh gravure roll, a second polyurethane emulsion of 2000 mPa·sec in which particles of a dialkyl phosphinic acid metal salt serving as a phosphorous-based flame retardant were dispersed was applied at 110 g/m² to the sliced surface of the dyed nappe artificial leather gray fabric, and the moisture was dried at 120° C. Note that the dialkyl phosphinic acid metal salt particles had a dispersed particle size (median diameter: D₅₀) of 4 μm, as measured by a laser diffraction/scattering particle size distribution measurement apparatus, a phosphorus atom content of 23.5 mass %, a solubility in water at 30° C. of less than 0.2 mass %, and a melting point and a decomposition temperature exceeding 250° C.

The second polyurethane emulsion contained 10 mass % of the second polyurethane and 28 mass % of the dialkyl phosphinic acid metal salt. The second polyurethane was a forcedly emulsified amorphous polycarbonate urethane having a 100% modulus of 1.0 MPa and including 4,4′-dicyclohexylmethane diisocyanate as the diisocyanate component.

Then, the napped artificial leather gray fabric that had been subjected to the flame retardant treatment was shrunk in the vertical direction (length direction) by 5.0% by being subjected to a shrinkage processing treatment at a drum temperature 120° C. and a transport speed of 10 m/min, and thereafter the surface thereof was subjected to a sealing treatment, thus obtaining a napped artificial leather including a suede-like napped surface. The napped artificial leather had a thickness of 0.4 mm, a basis weight of 225 g/m², and an apparent density of 0.56 g/cm³.

The napped artificial leather contained 10 mass % of the first polyurethane, 5 mass % of the second polyurethane, and 14.4 mass % of the dialkyl phosphinic acid metal salt particles. As a result, the napped artificial leather contained 3.4 mass % of the dialkyl phosphinic acid metal salt as a content ratio in terms of phosphorus atoms. The mass % in terms of phosphorus atoms to the total amount of the dialkyl phosphinic acid metal salt particles, the first polyurethane, and the second polyurethane was 11.5 mass %. The mass % in terms of phosphorus atoms to the total amount of the second polyurethane and the dialkyl phosphinic acid metal salt particles was 17.4 mass %.

Then, the obtained napped artificial leather was evaluated according to the following evaluation methods.

The results of the above evaluation are shown in Table 3 below.

TABLE 3 Example No. 12 13 14 15 16 17 Artificial Ultrafine Fineness 0.1 0.1 0.1 0.1 0.4 0.2 leather fibers (dtex) Resin PET PET PET PET PET PET First elastic Content (C) 10 9 19 11 10 10 polymer (mass %) Second elastic Content (D) 5 11 5 3 5 4 polymer (mass %) Phosphorous- Content (E) 14.4 13.6 12.6 8.9 14.5 14.4 based flame (mass %) retardant Compound Dialkyl Dialkyl Dialkyl Dialkyl Monoalkyl Aromatic particles phosphinic phosphinic phosphinic phosphinic phosphinic phosphinic acid acid acid acid acid acid metal salt metal metal metal metal ester salt salt salt salt Dispersed 4 4 4 4 2 5 particle size (D₅₀: μm) Water <0.2% <0.2% <0.2% <0.2% <0.1% <0.1% solubility (%: 30° C.) Melting point, >250° C. >250° C. >250° C. >250° C. >250° C. >250° C. or decomp- osition temperature in the absence of melting point (° C.) Phosphorus 23.5 23.5 23.5 23.5 28 15 atom content (mass %) (F) Content ratio of phosphorous- 17.4 13.0 16.8 17.6 20.8 11.7 based flame retardant particles in total amount of phosphorous- based flame retardant particles and second elastic polymer ((E) * (F)/(D + E)) (mass %) Content ratio of phosphorous- 11.5 9.5 8.1 9.1 13.8 7.6 based flame retardant particles in total amount of phosphorous- based flame retardant particles, first elastic polymer, and second elastic polymer ((E) * (F)/ (C + D + E)) (mass %) Content ratio in terms of 3.4 3.2 3.0 2.1 4.1 2.2 phosphorus atoms (E) * (F)/100(mass %) Phosphorous-based flame 4 4 4 4 2 5 retardant average particle size (SEM: μm) Thickness from back surface in 150 150 120 180 180 180 which phosphorous-based flame retardant particles and second elastic polymer are present (L: μm) Thickness of napped artificial 0.4 0.4 0.4 0.4 0.4 0.4 leather (T: mm) Ratio of thickness L to 38 38 30 45 45 45 thickness T (%) Basis weight g/m² 225 235 256 205 220 210 Apparent g/cm³ 0.56 0.56 0.59 0.54 0.56 0.56 density Surface quality appearance A A A A A A Burn test Burn distance 110 125 115 115 105 120 (Self-extin- (mm) guishing Self-exting- 0 1.5 1 0 0 0 properties) uishing time (sec) Drop self- 0 0 0 0 0 0 extinguishing time (sec) Composite Adhesive Starch- Vinyl Chlorine- Nitrile Starch-vinyl Starch- material vinyl acetate- metal- phenol- acetate- vinyl acetate- based salt based based acetate- based resin based resin resin based resin resin resin Interior backing material Calcium Calcium Gypsum Calcium Gypsum Fiber (back board) silicate silicate silicate cement Smoke test Smoke 5 6 8 6.5 14 6 density (SPR) Combustion Total heat 6.5 7 9.5 8 8 7 heat release test release (THR: MJ/ m² · 20 min) Peak heat 150 160 230 180 200 155 release rate (PHRR: kW/m²) Time for 0 0 7 2 5 0 which PHR exceeded 200 kW/m² (sec) Maximum 35 40 80 50 60 40 average rate of heat emission (MARHE) (kW/m²) Example No. 18 19 20 21 22 Artificial Ultrafine Fineness 0.2 0.001 0.001 0.1 0.1 leather fibers (dtex) Resin PET Ny Ny PET PET First Content (C) 9 31 25 10.2 10 elastic (mass %) polymer Second Content (D) 4 5 9 3.9 5 elastic (mass %) polymer Phosphorous- Content (E) 17.2 13.8 25.2 10.8 14.4 based (mass %) flame Compound Phosphoric Dialkyl Dialkyl Dialkyl Dialkyl retardant acid ester phos- phos- phos- phosphonic particles amide phinic acid phonic acid phonic acid acid metal metal salt metal salt metal salt salt Dispersed 8 4 4 4 4 particle size (D₅₀: μm) Water solubility <0.1% <0.1% <0.1% <0.1% <0.2% (%: 30° C.) Melting point, >250° C. >250° C. >250° C. >250° C. >250° C. or decomp- osition temp- erature in the absence of melting point (° C.) Phosphorus 17 23.5 23.5 23.5 23.5 atom content (mass %) (F) Content ratio of 13.8 17.3 17.3 17.3 17.4 phosphorous-based flame retardant particles in total amount of phosphorous-based flame retardant particles and second elastic polymer ((E) * (F)/(D + E)) (mass %) Content ratio of 9.7 6.5 10.0 10.2 11.5 phosphorous-based flame retardant particles in total amount of phosphorous-based flame retardant particles, first elastic polymer, and second elastic polymer ((E) * (F)/ (C + D + E)) (mass %) Content ratio in terms 2.9 3.2 5.9 2.5 3.4 of phosphorus atoms (E) * (F)/100 (mass %) Phosphorous-based 8 4 4 4 4 flame retardant average particle size (SEM: μm) Thickness from back 120 180 180 150 190 surface in which phosphorous-based flame retardant particles and second elastic polymer are present (L: μm) Thickness of napped 0.4 0.5 0.3 0.55 1.0 artificial leather (T: mm) Ratio of thickness L to 30 36 60 27 19 thickness T (%) Basis weight g/m² 230 225 128 300 300 Apparent g/cm³ 0.57 0.45 0.43 0.54 0.30 density Surface quality appearance A A A A A Burn test (Self- Burn distance 120 120 85 95 120 extinguishing (mm) properties) Self- 1 0 0 2 4 extinguishing time (sec) Drop self- 0 0 0 0 0 extinguishing time (sec) Composite Adhesive Vinyl Vinyl Vinyl Chlorine- Starch- material acetate- acetate- acetate- metal- vinyl based based based salt acetate- resin resin resin based based resin resin Interior backing material Calcium Calcium Gypsum Calcium Calcium (back board) silicate silicate silicate silicate Smoke test Smoke density 8 4 3 12 9 (SPR) Combustion Total heat 8 7 7 10 8 heat release release test (THR: MJ/m² · 20 min) Peak heat 210 220 200 240 200 release rate (PHRR: kW/m²) Time for 6 5 4 7 6 which PHR exceeded 200 kW/m² (sec) Maximum 80 60 50 85 85 average rate of heat emission (MARHE) (kW/m²)

Example 13

A napped artificial leather was obtained in the same manner as in Example 12 except that a second polyurethane emulsion containing 22 mass % of the second polyurethane and 28 mass % of the dialkyl phosphinic acid metal salt was used in place of the second polyurethane emulsion containing 10 mass % of the second polyurethane and 28 mass % of the dialkyl phosphinic acid metal salt, and the obtained napped artificial leather was evaluated. The results are shown in Table 3.

Example 14

A napped artificial leather was obtained in the same manner as in Example 12 except that a napped artificial leather having a first polyurethane content of 19 mass % was produced in place of the napped artificial leather having a first polyurethane content of 10 mass %, and the obtained napped artificial leather was evaluated. The results are shown in Table 3.

Example 15

A napped artificial leather was obtained in the same manner as in Example 12 except that the second polyurethane emulsion in which the dialkyl phosphinic acid metal salt particles serving as the phosphorous-based flame retardant were dispersed was applied at 60 g/m², instead of being applied at 110 g/m², and the obtained napped artificial leather was evaluated. The results are shown in Table 3.

Example 16

In Example 12, a non-woven fabric in which fiber bundles each including six ultrafine fibers of 0.4 dtex were three-dimensionally entangled was formed in place of the non-woven fabric in which fiber bundles each including 25 ultrafine fibers of 0.1 dtex were three-dimensionally entangled. In addition, as the first polyurethane, a self-emulsified polyurethane having a mass ratio between the amorphous polycarbonate polyol and the polyether polyol of 60/40, and having a 100% modulus of 3.0 MPa was used in place of the self-emulsified amorphous polycarbonate urethane having a 100% modulus of 3.0 MPa and including 4,4′-diphenylmethane diisocyanate as the diisocyanate component. Furthermore, the monoalkyl phosphinic acid metal salt shown in Table 3 was used in place of the dialkyl phosphinic acid metal salt as the phosphorus-based flame retardant particles. Otherwise, a napped artificial leather was obtained in the same manner, and the obtained napped artificial leather was evaluated. The results are shown in Table 3.

Example 17

A napped artificial leather was obtained in the same manner as in Example 12 except that the aromatic phosphonic acid ester shown in Table 3 was used in place of the dialkyl phosphinic acid metal salt as the phosphorous-based flame retardant particles, and the obtained napped artificial leather was evaluated. The results are shown in Table 3.

Example 18

A napped artificial leather was obtained in the same manner as in Example 12 except that the phosphoric acid ester amide shown in Table 3 was used in place of the dialkyl phosphinic acid metal salt as the phosphorous-based flame retardant particles, and the obtained napped artificial leather was evaluated. The results are shown in Table 3.

Example 19

In Example 12, polyethylene and 6-nylon were mixed at a mass ratio of 50/50, and molten, and the molten resins were supplied to a blend spinning spinneret, and discharged from the nozzle holes. The average number of islands of the resulting fibers was approximately 600, and the fibers were stretched, to give fibers of 5.5 dtex. The fibers were crimped, and thereafter cut into 51 mm and carded, thus obtaining a staple web having a basis weight of 100 g/m². This web was laid in six layers using a cross lapper apparatus, to form a superposed web, and an oil solution was sprayed thereto, and thereafter the web was needle punched at a density of 1500 punch/cm², followed by hot pressing, to obtain a fiber-entangled body having an apparent density of 0.40 g/cm³ and a thickness of 1.2 mm. Then, the fiber-entangled body was impregnated with a polyurethane dissolved in N,N-dimethylformamide at the mass ratio shown in Table 3 as the first polyurethane, the polyurethane including a diisocyanate component composed of 4,4′-diphenylmethane diisocyanate, and a polymer polyol composed of a polycarbonate polyol and a polyester polyol at a mass ratio of 75/25, and having a 100% modulus of 5.0 MPa. Thereafter, the fiber-entangled body was immersed in a liquid mixture of N,N-dimethylformamide and water for coagulation, and then the polyethylene was extracted with toluene, and dried. After that, a napped artificial leather was obtained in the same manner as in Example 12 except that dye was changed from the disperse dye to a metal complexed dye, and the obtained napped artificial leather was evaluated. The results are shown in Table 3.

Example 20

A napped artificial leather having a thickness of 0.3 mm, a basis weight of 128 g/m² and an apparent density of 0.43 g/cm³ was obtained in the same manner as in Example 19 except that the number of layers in which the staple web was laid was changed from six to four, and the obtained napped artificial leather was evaluated. The results are shown in Table 3.

Example 21

A napped artificial leather having a thickness of 0.55 mm, a basis weight of 300 g/m², and an apparent density of 0.54 g/cm³ was obtained in the same manner as in Example 12 except that the web was laid in 10 layers using a cross lapper apparatus so as to have a total basis weight of 330 g/m², and the obtained napped artificial leather was evaluated. The results are shown in Table 3.

Example 22

A napped artificial leather having a thickness of 1.0 mm, a basis weight of 300 g/m2, and an apparent density of 0.30 g/cm³ was obtained in the same manner as in Example 12 except that the web was laid in 32 layers, instead of 8 layers, using a cross lapper apparatus, that the web was subjected to the impregnation so as to have a first polyurethane content of 12 mass %, and that the napped artificial leather gray fabric was not subjected to the shrinkage treatment , and the obtained napped artificial leather was evaluated. The results are shown in Table 3.

Comparative Example 6

A napped artificial leather was obtained in the same manner as in Example 12 except that a second polyurethane emulsion containing 10 mass % of the second polyurethane and 6.8 mass % of the dialkyl phosphinic acid metal salt was used in place of the second polyurethane emulsion containing 10 mass % of the second polyurethane and 28 mass % of the dialkyl phosphinic acid metal salt, and the obtained napped artificial leather was evaluated. Note that the viscosity of the aqueous dispersion including the phosphorous-based flame retardant particles and the second elastic polymer was 100 mPa·sec. The results are shown in Table 4.

TABLE 4 Comparative Example No. Com. Com. Com. Com. Com. Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Artificial Ultrafine Fineness 0.1 0.1 0.1 0.1 0.6 leather fibers (dtex) Resin PET PET PET PET PET First Content (C) 11 10 10 10 10 elastic (mass %) polymer Second Content (D) 6 0 5 5 5 elastic (mass %) polymer Phosphorous- Content (E) 3.9 15.2 14.4 14.4 8.2 based (mass %) flame Compound Dialkyl Ammonium Ammonium Aromatic Dialkyl retardant phosphinic poly- poly- phosphoric phosphinic particles acid metal salt phosphate phosphate acid ester acid metal salt Dispersed 4 20 20 0.5 4 particle size (D₅₀: μm) Water <0.2% 0.5 0.5 <0.2% <0.2% solubility (%: 30° C.) Melting >250° C. >250° C. >250° C. 115° C. >250° C. point, or decomposition temperature in the absence of melting point (° C.) Phosphorus 23.5 31 31 10 23.5 atom content (mass %) (F) Content ratio of phosphorous- 9.3 31.0 23.0 7.4 14.6 based flame retardant particles in total amount of phosphorous-based flame retardant particles and second elastic polymer ((E) * (F)/(D + E)) (mass %) Content ratio of phosphorous- 4.4 18.7 15.2 4.9 8.3 based flame retardant particles in total amount of phosphorous-based flame retardant particles, first elastic polymer, and second elastic polymer ((E) * (F)/ (C + D + E)) (mass %) Content ratio in terms of 0.9 4.7 4.5 1.4 1.9 phosphorus atoms (E) * (F)/100(mass %) Phosphorous-based flame 4 20 20 Non- 4 retardant average particle particulate size (SEM: μm) Thickness from back surface 300 50 50 200 200 in which phosphorous-based flame retardant particles and second elastic polymer are present (L: μm) Thickness of napped 0.4 0.4 0.4 0.4 0.75 artificial leather (T: mm) Ratio of thickness L 75 13 13 50 27 to thickness T (%) Basis weight g/m² 200 210 225 225 390 Apparent g/cm³ 0.5 0.53 0.56 0.56 0.5 density Surface quality appearance B B, D D C A Burn test Burn distance 300 140 165 300 260 (Self- (mm) extinguishing Self- 30 7 9.5 38 24 properties) extinguishing time (sec) Drop self- 8 0 2.5 15 8 extinguishing time (sec) Composite Adhesive Starch-vinyl Starch-vinyl Starch-vinyl Starch-vinyl Starch-vinyl material acetate-based acetate-based acetate-based acetate-based acetate-based resin resin resin resin resin Interior backing Calcium Gypsum Gypsum Calcium Calcium material (back board) silicate silicate silicate Smoke test Smoke density 18 8 15 16 16 (SPR) Combustion Total heat 20 9 16 24 18 heat release release (THR: test MJ/m² · 20 min) Peak heat 340 200 270 360 300 release rate (PHRR: kW/m²) Time for 16 8 14 18 18 which PHR exceeded 200 kW/m² (sec) Maximum 160 60 120 180 110 average rate of heat emission (MARHE) (kW/m²)

Comparative Example 7

A napped artificial leather was obtained in the same manner as in Example 12 except that an aqueous dispersion containing 28 mass % of ammonium polyphosphate having a dispersed particle size of 20 μm was used in place of the second polyurethane emulsion containing 10 mass % of the second polyurethane and 28 mass % of the dialkyl phosphinic acid metal salt, and the obtained napped artificial leather was evaluated. Note that the viscosity of the aqueous dispersion including the phosphorous-based flame retardant particles and the second elastic polymer was 100 mPa·sec. The results are shown in Table 4.

Comparative Example 8

A napped artificial leather was obtained in the same manner as in Example 12 except that the first polyurethane that was the self-emulsified amorphous polycarbonate urethane having a 100% modulus of 3.0 MPa and including 4,4′-dicyclohexylmethane diisocyanate as the diisocyanate component was changed to a first polyurethane that was a self-emulsified amorphous polycarbonate urethane having a 100% modulus of 2.0 MPa and including 1,6-hexamethylene diisocyanate as the diisocyanate component, and also that the ammonium polyphosphate shown in Table 1 was used in place of the dialkyl phosphinic acid metal salt as the phosphorous-based flame retardant particles, and the obtained napped artificial leather was evaluated. The results are shown in Table 4.

Comparative Example 9

A napped artificial leather was obtained in the same manner as in Example 12 except that the aromatic phosphoric acid ester shown in Table 4 was used in place of the dialkyl phosphinic acid metal salt as the phosphorous-based flame retardant particles, and the obtained napped artificial leather was evaluated. The results are shown in Table 4. Note that the phosphorous-based flame retardant was treated in the form of an aqueous dispersion during the flame retardant treatment. However, as a result of observation of the napped artificial leather, the phosphorous-based flame retardant had formed a resin film, and was not in the particulate form.

Comparative Example 10

A napped artificial leather was obtained in the same manner as in Example 12 except that the number of the island components formed with the spinneret was changed from 25 to 4, and that the number of layers in which the web of the napped artificial leather was laid was changed from 8 to 16, and the obtained napped artificial leather was evaluated. The results are shown in Table 4.

Referring to Tables 3 and 4, all of the artificial leather base materials obtained in Examples 12 to 22 had a favorable surface quality appearance and a flexible texture, and furthermore, exhibited favorable self-extinguishing properties, and reduced smoke generation and combustion heat release, thus realizing napped artificial leathers having a high level of flame retardancy. On the other hand, in the case of the napped artificial leather obtained in Comparative Example 6, which included a smaller amount of the phosphorous-based flame retardant particles, and in which the flame retardant particles were present even in the interior, the phosphorous-based flame retardant was exposed on the surface, resulting in deterioration in the surface quality appearance. In the case of the napped artificial leather obtained in Comparative Example 7, for which ammonium polyphosphate was used as the phosphorous-based flame retardant particles, bleeding had occurred over time, resulting in a poor appearance. In the case of the napped artificial leather obtained in Comparative Example 8, bleeding had occurred over time, resulting in a poor appearance. Comparative Example 9, in which the phosphorous-based flame retardant particles were changed to an aromatic phosphoric acid ester, had a hard texture. Comparative Example 10, in which the napped artificial leather had a high fineness and also a high basis weight, was inferior in flame retardancy. 

1. A napped artificial leather comprising: a fiber-entangled body comprising ultrafine fibers having a fineness of 0.5 dtex or less; an elastic polymer impregnated into the fiber-entangled body; and phosphorous-based flame retardant particles attached to the elastic polymer; wherein: the napped artificial leather having has a thickness of 0.25 to 1.5 mm; the napped artificial leather comprises including a main surface that is a napped surface formed by napping the ultrafine fibers and a back surface opposite to the main surface; the phosphorous-based flame retardant particles are locally present in a range of a thickness of 200 μm or less from the back surface; the phosphorous-based flame retardant particles have an average particle size of 0.1 to 30 μm, a phosphorus atom content of 14 mass % or more, a solubility in water at 30° C. of 0.2 mass % or less, and a melting point, or, in the absence of a melting point, a decomposition temperature, of 150° C. or more; and a content ratio of the phosphorous-based flame retardant particles in the napped artificial leather is 1 to 6 mass % as a content ratio in terms of phosphorus atoms.
 2. The napped artificial leather according to claim 1, wherein: the elastic polymer comprises a polyurethane that is a reaction product of a polyurethane raw material comprising a polymer polyol, an organic polyisocyanate, and a chain extender; the polymer polyol comprises 60 mass % or more of a polycarbonate polyol, and has an average number of repeating carbon atoms excluding a reactive functional group, of 6.5 or less; and the organic polyisocyanate comprises at least one selected from the group consisting of 4,4′-dicyclohexylmethane diisocyanate and 4,4′-diphenylmethane diisocyanate.
 3. The napped artificial leather according to claim 1, wherein the napped artificial leather has a basis weight of 100 to 300 g/m².
 4. The napped artificial leather according to claim 1, wherein the phosphorous-based flame retardant particles include comprise at least one compound selected from the group consisting of an organic phosphinic acid metal salt, an aromatic phosphonic acid ester, and a phosphoric acid ester amide.
 5. The napped artificial leather according to claim 1, wherein the phosphorous-based flame retardant particles comprise at least one selected from the group consisting of a dialkyl phosphinic acid metal salt and a monoalkyl phosphinic acid metal salt.
 6. The napped artificial leather according to claim 1, wherein 90 to 100 mass % of the phosphorous-based flame retardant particles are present in the range of a thickness of 200 μm or less from the back surface.
 7. The napped artificial leather according to claim 1, wherein a ratio of a thickness of a region of the napped artificial leather in which the phosphorous-based flame retardant particles are locally present to an overall thickness of the napped artificial leather is 10 to 60%.
 8. The napped artificial leather according to claim 1, wherein a content ratio of the phosphorous-based flame retardant particles relative to a total amount of the phosphorous-based flame retardant particles and the elastic polymer is 5 to 20 mass % in terms of phosphorus atoms.
 9. The napped artificial leather according to claim 1, wherein: the elastic polymer comprises a first elastic polymer that is present throughout a thickness cross section of the napped artificial leather, and a second elastic polymer that is locally present in the range of a thickness of 200 um or less from the back surface; and the phosphorous-based flame retardant particles are attached to the second elastic polymer.
 10. The napped artificial leather according to claim 9, wherein a content ratio of the phosphorous-based flame retardant particles relative to a total amount of the phosphorous-based flame retardant particles and the second elastic polymer is 10 to 30 mass % in terms of phosphorus atoms.
 11. A composite material comprising: the napped artificial leather according to claim 1; and an interior backing material bonded to the back surface of the napped artificial leather with an adhesive.
 12. The composite material according to claim 11, wherein the composite material has a total heat release (THR) of 10 MJ/m² or less.
 13. The composite material according to claim 11, wherein the composite material has a peak heat release rate (PHRR) of 250 kW/m² or less.
 14. The composite material according to claim 11, wherein the composite material has a maximum average rate of heat emission (MARHE) of 90 kW/m² or less.
 15. The napped artificial leather according to claim 2, wherein the phosphorous-based flame retardant particles comprise at least one selected from the group consisting of a dialkyl phosphinic acid metal salt and a monoalkyl phosphinic acid metal salt.
 16. The napped artificial leather according to claim 6, wherein the phosphorous-based flame retardant particles comprise at least one selected from the group consisting of a dialkyl phosphinic acid metal salt and a monoalkyl phosphinic acid metal salt.
 17. The napped artificial leather according to claim 7, wherein the phosphorous-based flame retardant particles comprise at least one selected from the group consisting of a dialkyl phosphinic acid metal salt and a monoalkyl phosphinic acid metal salt.
 18. The napped artificial leather according to claim 9, wherein the phosphorous-based flame retardant particles comprise at least one selected from the group consisting of a dialkyl phosphinic acid metal salt and a monoalkyl phosphinic acid metal salt. 